Continuous-flow electrolyzers allow CO2 reduction at industrially relevant rates, there are still several challenges to be solved before the technology can be industrialized. A major goal within the CO2 electrolysis community is to replace the generally used Ir anode catalyst with a more abundant material, which is stable and active for water oxidation under process conditions. In this vein, I will first give an overview on the anode catalysts which have been studied beyond Ir. In the second part of my talk, I will compare the operation of electrolyzer cells with Ir and Ni (as a potential alternative) anodes and demonstrate that while Ir is stable under process conditions, the degradation of Ni leads to a rapid cell failure. This is caused by two parallel mechanisms: (i) a pH decrease of the anolyte to a near neutral value and (ii) the local chemical environment developing at the anode (i.e., high carbonate concentration). The latter is detrimental for zero-gap electrolyzer cells only, but the first mechanism is universal, occurring in any kind of CO2 electrolyzer after prolonged operation with recirculated anolyte. As a conclusion, I will present the feature what an anode catalyst has to fulfill, to be successfully employed in CO2 electrolyzers.

Anode catalysts in CO2 electrolysis: Challenges and untapped opportunities

ACS Spring 2022

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